Cleaning tile at the waterline is one of those dirty deeds that go along with pool ownership. To refresh your memory, the waterline—or water line—is the area of a swimming pool or spa where the water meets the tile, or the fill line (not that there's an actual line). That's assuming you don't want to pay a pool service company to bead-blast it clean.
What Is That Stuff, Anyway?
The dirty stuff that discolors a pool's water line is usually either scale or stain. If you have hard-water deposits or stains in sinks or tubs inside your house, they might be on your pool surfaces too. After water evaporates, scaling can occur when calcium deposits cling to the sides of a pool. It shows up as white or gray "scum" and is difficult to remove. The two main types of scaling in a pool are:
- Calcium silicate: This greyish-white stuff is the harder of the two, primarily because it has been on your pool's surfaces longer than calcium carbonate. If it does not react with an application of muriatic acid, then it's most likely silicate and will have to be cleaned with a pumice stone.
- Calcium carbonate: A pumice stone can also be used for the flaky white stuff on your pool's surfaces. You will know it is calcium carbonate if it bubbles up after using muriatic acid.
Pool staining can show up in a variety of colors and occurs as the result of a chemical imbalance reacting with the pool's surfaces.
Tackling Staining and Scaling
For starters, working on it in small increments of time—like when you're outside watching your children in the pool—is better than allowing the algae and dirty gross stuff to accumulate. If you prefer to try a chemical-free method whenever possible, there are a few cleaning agents you may already have, without having to go spend more money.
If the dirt and grime at the water line is minimal, scrub at it with a used toothbrush and one of these "cleaners":
If it has gotten to a state beyond the mild, natural stuff, put on a pair of rubber gloves and use a tile cleaner and a pumice stone, which you can buy at pool supply stores or any hardware store. Since you've let it go this far, you might want to try a super cleaner that will really cut through the scale and scum: it's called The Works. According to its website, the brand has been around for more than 50 years. I'm not sure what's in it, and not sure I want to know, but I've cleaned a toilet with some bad rust stains (don't ask) and a pumice file, and that combo did the job. Another product by the same company, called Limeosol, is made to cut through and safely clean lime, rust, calcium, and water stains.
Make sure to use The Works or any other tile cleaner before you use any pool chemicals, and wait a few days after, just to be on the safe side.